The present invention relates generally to papermaking apparatus having variable, or adjustable, dewatering elements, and more particularly to variable turbulation blades.
In the manufacture of paper, paper stock is carried by a conveyor over dewatering elements. Some of the dewatering elements have a geometry or position which produces turbulence in the paper stock to produce selected action in the paper stock. In the past, such turbulence has been produced by providing various foils or turbo blades in selected positions over which the conveyor and the paper stock move. The angular positioning of the foils, or turbo blades is selected to produce the turbulation action desired.
Prior turbo blades have been provided which have a fixed in-going angle between a flat leading portion of the blade and the conveyor to obtain a stock pulse of selected magnitude. However, such prior turbo blades generally have not been coupled with adjustment mechanism which allows the in-going angle for the blade to be varied, or adjusted, while the blade is adjacent the conveyor.
Further, prior turbo blades having fixed in-going angles have not permitted the fine adjustment of turbulating pulses as may be desired.
Some prior apparatus has provided mechanism for adjusting the angle of a foil contacting the underside of the conveyor to control the water removal rate of the dewatering element. One such example as shown in U.S. Pat. No. 5,169,500 of Mejdell issued Dec. 8, 1992. However, the dewatering elements disclosed therein generally are configured, such that there is little opportunity for providing variation in in-going angles of the leading portion of the foil.
It is an object of the present invention to provide an improved system and method for papermaking in which a plurality of dewatering elements, including variable turbulation blades, are adjustable to provide a paper sheet of improved characteristics.
Another object of the present invention is to provide such a system and method in which turbulation blades which engage the surface of the conveyor carrying the paper stock to control the water removal rate with adjusting mechanism to adjust the in-going angle of a blade.
An additional object of the present invention is to provide such a system which includes a moveable turbulation blade which is connected to a fixed member by a cam mechanism for adjusting the in-going angle of the blade relative to the conveyor for the paper stock.
Another object of the invention is to provide a variable pulse turbulation blade having an in-going angle relative to the conveyor which is adjustable to provide a more uniform paper sheet for different grades of paper while maintaining the height of the blade substantially constant relative to the conveyor.
Yet another object of the invention is to provide paper stock turbulation apparatus for agitation of paper stock carried on a conveyor to form a paper sheet which includes a turbulation blade positioned adjacent the conveyor and having a variable in-going angle formed between the paper sheet conveyor and a leading portion of the upper surface of the blade and adjustment mechanism for moving the blade to different positions to adjust the in-going angle of the blade relative to the conveyor, thereby to control the turbulation of the paper stock on the conveyor while the turbulation blade is positioned adjacent the conveyor.
A still further object of the invention is to provide such paper stock turbulation apparatus in which the leading portion of the blade includes a plurality of angularly disposed areas which extend along the leading portion and form different in-going angles with the conveyor.
Yet another object of the invention is to provide a turbulation blade for a papermaking machine having an elongate substantially rigid member with an upper surface over which a conveyor may run and a leading edge extending along one side thereof, with the upper surface having a leading portion adjacent the leading edge which includes a plurality of flat surface areas, which extend along the leading portion and form different angles with a plane extending tangent to the upper surface of the blade.
Another object of the invention is to provide a turbulation blade for a papermaking machine having an elongate substantially rigid member with an upper surface over which a conveyor may run and a leading edge extending along one side thereof, with the upper surface having a leading portion adjacent the leading edge which is curved downwardly from a plane extending tangent to the upper surface of the blade and including a plurality of different radii of curvature in successive portions of the leading portion which extend along the leading portion.
Other objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof and from the attached drawings.